Method of annealing



June 14, 1938. L. wlLsoN METHOD OF ANNEALING Filed June l5, 1935 MM. QM.

Patented June 14,1938

` UNrrEzo` STATES 2,120,319 METHOD F ANNEALING Lee Wilson,` Cleveland.Ohio Application June 15, 1935, ASerial No. 26,853

1 Claim.

' My invention relates to the art of treating metal and, in particular,to the annealing of thin gauge metal in strip form. The annealing ofstrip has always been attended with considerable diiilculty heretofore.About the best procedure evolved so far is the annealing of-strip incoils in which it is reeled after cold rolling, either in conventionalannealing boxes or in boxes particularly designed to receive roundcoils. The

boxes may be heated by heating means mounted therein, or may be bodilymovable into a heating furnace. In either case, the annealing process isvery slow and the efficiency is not very high, particularly as to thestacking of coils in conventional annealing boxes. A large amount ofequipment is necessary because of the slowness of the process. and thismakes the operation very expensive.

My invention overcomes the aforementioned objectionsto the presentpractice of annealing strip and provides, for the ilrst time, so far asI am aware, a practical, inexpensive and rapid method of annealingstrip. In accordance with my invention, I anneal strip by heating it tothe required temperature while in strand form. I coil the strip whilestill hot and cool it slowly in the coiled form. The heating, coilingandcooling operations are preferably conducted in the absence ofatmospheric oxygen. I stitch togather successive strips being annealedand sever the strip when a suillcient amount thereof has been coiledfromthe strand I also'prefer to cool the strip slightly before coilingto prevent stick.

vice and a cooling chamber; and i Figure 2 is a sectional view takenalong the line II II oi' Figure 1. .f

Referring now in detail to the drawing. 'ah annealing furnace I0 of theso-called tunnelf type. i has side walls il, a roof I2 and a hearth i2comeVy My invention. also includes a.

Figure 1A is a similar view of the coiling de posed of refractorymaterial assembled within a structural framework (not shown). Theentrance end of the furnace has a restricted port or opening I4 normallyclosed by flexible flaps I5 which arel displaceable by strip materialin- 5 dicated at I8 moving into the furnace. The discharge end of thefurnace is-provided with an opening or port I1.

. The interior of the furnace is divided by a transverse partition wallI8 into a heating cham- 10, ber I8 and a cooling chamber 2B. Pinch rollstands 2i and 22 located at the entrance end of the furnace\,andadjacent the discharge opening i1, respectively, serve to feed the stripthrough the furnace in the directionof the arrow 15.

23. Conveyor'rollers 24 are mounted at intervals along the length of thefurnace to support vthe material being passed therethrough.

The heating chamber i9 is provided with a plurality of heat exchangetubes 25. In the particular formv of the invention illustrated, thetubes extend transversely ofv the furnace chamber and penetrate the sidewalls Il' thereof at points above the rolls 24. Any otherv suitablearrange- `ment of the tubes may, however, be employed. 25

Burners 28 extend into the tubes adjacent one end, the other e'nd ofeach tube bein'g open for vdischarging combustion gases. A damper 21 ismounted adjacent' the discharge end of ,each tube for controlling.theflow of gases therethrough. Fuel is supplied tothe burners 26 fromheaders 2l'and air for combustion is induced throughthe open ends of thetubes in which the burners are mounted.

The cooling chamber l20 is also provided with conveyor rolls 24. Heatexchangeltubes 20a extend transversely ofthe furnace above the conveyorrolls and are Yconnected to any suitable source of cooling medium, suchas air. The function of the tubes 20a is to cool` the material I6 40slightly before it emerges from the furnace.

A portable coller 2l comprises a frame 30 preferably provided withwheels 3i for easy movement, and an enclosure 22 of any suitableconstruction. A .coller 23 is mounted on the 45 frame 3l within theenclosure 22. The construction of coilersis well known and requires nodetailed disclosure.

At one side, the enclosure I2 is providedwith la` tubular projection 24adapted to enter the port 50 I1 and make a substantially gas-tightconnection therewith The enclosure 321s also provided with a door 2lwhich may be hinged or slidably mounted for opening.

A cooling chamber' It of any suitableconstruction and preferably havinga door 31, is disposed in any desired location, preferably adjacent thefurnace l 0. 'I'he function o'f the cooling chamber is to receive coilsof strip for slow cooling after they have been heated to the annealingtemperature and, so long as it performs its function, the specificconstruction thereof 'is not of great moment.

The method of my invention will now be explained referring to theapparatus already described.l Strip metal is usually rolled inrelatively long lengths and coiled when the rolling is completed. It maybe assumed, therefore, that the material I6 entering the furnace I0 isunwound from a. coil mounted on an uncoiler. Alternatively, the stripmay be fed directly from the mill to the furnace. The first length ofstrip may be fed through the furnace by means of a rigid leader in amanner Well known to the art, and successive lengths of strip may beattached by spot welding or otherwise, to the trailing end of thepreceding length, so as to form a continuous movement of successivestrips through the furnace. The heating chamber of the furnace ispreferably maintained at a temperature of 1500 F. to 1800 F. The stripis heated to this temperature gradually as it passes through thefurnace, and the length of the furnace and therate oftravel of 'thematerial therethrough may be coordinated to insure the desired heatingof the strip. As the strip enters the cooling chamber 20, it is cooledrapidly to about 1250 F. or any other desired temperature. I preferablymaintain a non-oxidizing atmosphere within the chambers I9 and 20 of thefurnace to prevent oxidation of the strip by atmospheric oxygen. .Thisdeoxidizing atmosphere also illls the enclosure 32 of the coiler 29 byvirtue of the connection 34 between the enclosure and the coolingchamber 20. 'I'he strip on emerging from the furnace passes through thetubular connection 34 and on to the coiler 33. The strip is thus coiledat a temperature of substantially 1250 F., in a non-oxidizingatmosphere. When a sumcient amount of strip has been coiled, the coiler29 is pulled away from the furnace and the strip severed adjacent theport I1. 'I'he coiler is then moved to the cooling chamber 36, the door31 of which is opened, to permit the coil formed by the coiler 33 to beremoved therefrom through the door 35 and deposited in the coolingchamber. If desired, the open end of the tubular projection 34 may betemporarily closed by any suitable cover while the coiler is beingremoved to the cooling chamber 36. When the hot coil has been placed inthe cooling chamber, the coiler is returned to the position shown inFigure 1 and a new coil is started.

After a period of slow cooling in the chamber 36, the annealing iscompleted and the coils may be removed therefrom for furthermanufacturing operations.

The rapid cooling step of the process is not necessary when annealingcertain material, such as silicon steel or corrosion-resistant steelalloys, because such materials are not subject to sticking of adjacentturns of the coil at the normalizing temperature above mentioned, viz.,around 1500 to 1800 F.

It will be apparent that the invention described in the foregoingconstitutes a marked improvement over present processes of annealing.The rate of performing the annealing operation is greatly increased andonly a relatively small amount of equipment is necessary. Since thematerial passes through the furnace rather rapidly, the tonnage outputis high. The chamber in which the coils are slowly cooled may be ofrelatively inexpensive construction and easily designed for almost anydesired capacity. The invention also lends itself admirably to brightannealing, since all the operations can be conducted in the absence ofatmospheric oxygen.

The portable coiler makes it possible to conduct the coolingoperation ina non-oxidizing atmosphere and thereby protect the strip being coiledfrom atmospheric oxidation. The coiler also serves as a convenient meansfor transporting coils from the furnace to the cooling chamber.

The indirect heating of the annealing furnace is advantageous in that itinsures a substantially uniform temperature throughout the furnace andprevents overheating of or injury to the material being treated, whichmight result from direct contact of the hot combustion gases therewith.

Although I have illustrated and described herein but one preferred formand practice of the invention, it will be apparent that any changes inthe apparatus and method disclosed may be made Without departing fromthe spirit of the invention or the scope of the appended claim.

I claim:

A method of annealing a steel strip including the steps of heating thestrip in strand form to a temperature of about'1300" F. or above,cooling the strip rapidly to a lesser elevated temperature butsufficiently below 1300 F. to prevent sticking of turns when coiled,coiling the strip at said temperature, and thereafter cooling the coiledstrip slowly to room temperature.

LEE WILSON.

